1. Field of the Invention
This invention relates generally to methods of and apparatus for providing communication between different pressure environments. More particularly, this invention relates to the establishment of fluid-tight connections between concentric tubes or the like which provide access to the interior of a pressure vessel. Accordingly, the general objects of the present invention are to provide novel and improved apparatus and methods of such character.
2. Brief Description of the Prior Art
In numerous industrial applications, particularly in nuclear power related technology, penetrations are required into large vessels within which processes occur at high pressures. For example, in a nuclear reactor vessel, penetrations are necessary to provide openings through which control rods or instrumentation may be inserted into the reactor core. These penetrations typically comprise "nozzles" which are welded to the reactor pressure vessel wall to provide support structures on which equipment associated with manipulation of the control rods or instruments may be mounted.
In many applications, a separate column or guide conduit is situated concentrically within the nozzle structure. The separate column or conduit is attached internally to the nozzle or to other structure within the vessel. Equipment mounted on or in the column must occasionally be removed for maintenance or repair and thus the ability to disassemble the column from the nozzle is required. However, during normal operation, a fluid-tight closure or connection must be provided between the nozzle and the concentrically received column to prevent leakage of radioactive or otherwise environmentally disruptive fluid from within the vessel.
In one known method for connecting and sealing a column to a nozzle of a reactor vessel, metal to metal seals are actuated by "Marman" clamps (a product of the Aeroquip Corporation of Los Angeles, Calif.). Typically, in this prior method a hydraulic tool is attached to a groove or other mounting means in the nozzle or to an adaptor member on the nozzle for seating the seals. After the seals are seated, the "Marman" clamp halves are bolted together to maintain the seal in a compressed state. The hydraulic tool is then removed and an autoclave-type metal seal is compressed by torquing several jacking screws around the perimeter of the nozzle. This latter technique has the disadvantages of being relatively time-consuming, which can be a very important consideration where the potential for exposure to radioactivity is present, and of requiring the maintenance of relatively close manufacturing tolerances.
In U.S. Application Ser. No. 609,919, now U.S. Pat. No. 4,655,483, filed May 14, 1984, entitled "Boundary Seal for Pressure Penetration", the referenced application being assigned to the assignee of the present invention, a connector device provides a primary pressure boundary between a nozzle and a column concentrically disposed therein. The connector device includes a closure member for compressing a seal ring against the end of the nozzle. The closure member includes a hub portion which defines an annular space between the closure member and the column. Packings are inserted in this annular space and compressed by means of a drive unit which includes a drive sleeve and an actuator nut threaded to an upper portion of the sleeve. A split-ring type collar is clamped to the column to provide support for the column. Rotation of the actuator nut loads the column thus causing it to be longitudinally displaced relative to the closure member until a tight connection is made. Continued actuation of the nut advances the drive sleeve along the annular space to compress the gasket to thereby complete the fluid-tight connection. While the boundary seal of the referenced application can be installed in a relatively short time when compared to previous devices of like character, it nevertheless requires substantial effort to install the connector, particularly the collar clamp which has eight bolts to tighten. Further, this boundary seal assembly does not completely insure against the column assembly accidentally moving upwardly or downwardly during the assembly process.